Recent developments, such as the explosion of online pharmacies and supply chain issues, have made it easier for counterfeiters to profit from fake or adulterated medications. Now, researchers reporting in ACS Central Science have created edible tags with fluorescent silk proteins, which could be placed directly on pills or in a liquid medicine. The codes within the tags can be read by a smartphone app.
In the past, scientists have developed fluorescent synthetic materials as tracking codes, but substances such as microfibers and nanoparticles are potentially unsafe to consume. That’s why researchers Seong-Wan Kim, Young Kim and colleagues turned their attention to silk, an edible and “generally recognized as safe” material.
To help combat illegitimate online pharmacies and instill trust in consumers, the researchers genetically modified silkworms to produce silk fibroins—edible proteins that gives silk fibers their strength—with either a cyan, green or red fluorescent protein attached. They dissolved the fluorescent silk cocoons to create fluorescent polymer solutions, which they applied onto a thin, 9-mm-wide film of white silk in a grid. Shining blue violet, blue, and green light onto the grid revealed the 3D cyan, green and red square patterns, respectively.
Using optical filters over the phone’s camera, an app the team designed can scan the fluorescent pattern, decoding the digitized key using a deep learning algorithm and opening up a webpage, which could host information about the drug’s source and authenticity.
Covering all their bases, the researchers also examined a solution for liquid-based medicine. Because some liquid medications are alcohol-based, the researchers placed a coded silk film in a clear bottle of Scotch whisky, and found that the fluorescent code was still readable with the app.
Finally, the researchers showed that the fluorescent silk proteins are broken down by gastrointestinal enzymes, suggesting that the silk codes are not only edible, but also can be digested by the body.
Photo: Silkworms can produce edible, fluorescent silk cocoons (left side of left image); the proteins from the cocoons can be used in codes (right) to verify the authenticity of medications. Credit: Adapted from ACS Central Science 2022, DOI: 10.1021/acscentsci.1c01233